The invention relates generally to electric discharge machining (EDM). More particularly, the invention relates to an EDM device using a rotating circular blade.
Machining difficult metals or alloys such as high resistive nickel alloys (e.g., Inconel) is an ongoing challenge for manufacturers. Conventional machining is difficult for these metals because they are harder and tougher than other alloys. Non-conventional approaches include laser machining, electro-chemical machining, and electrical discharge machining, some of which are relatively slow, require large energy consumption and present other challenges. EDM die sinking has been used to make a variety of structures out of these materials in small volumes. EDM die sinking typically involves placing a workpiece into a tank of fluid such as hydrocarbon-based oil. A die electrode having a mirror image of the desired shape for the workpiece is driven by a ram into close proximity to the workpiece, and an electric pulse is then repetitively applied to the gap between the die electrode and workpiece to cause electric discharges that precisely remove material from the workpiece. EDM die sinking has the capability of machining difficult metals or alloys without high cutting force and hard tools, which makes the process cost efficient and less demanding than conventional machining techniques. Although EDM die sinking is an attractive process for machining these alloys, a number of challenges currently limit its use.
Some other EDM-based approaches employ a rotating grinding surface tool. One challenge with any of the EDM-based approaches is that they remove material in the form of particles, which makes the processes very slow. Wire-based EDM is also employed, but is incapable of forming some complex parts in 3-dimensional shapes, such as concave forms on an airfoil. The power input to a wire electrode is limited to prevent wire breakage, which limits the cutting speed to an unsatisfactory rate.